Bring a pot of water to a boil and add green beans. Simmer for three minutes until they are crisp-tender, then drain and run them under cool water so they stop cooking.
Bring 3 cups of water to a boil and add farro and salt. Cover the pot, reduce to a simmer and cook for 30 minutes or until farro is tender, adding a little more water if it needs it. Drain.
Place green beans and farro in a mixing bowl. Add vinegar and olive oil and toss.
Taste and season with salt and pepper to your liking. Add crumbled feta cheese and give one more gentle toss. Grind a little more pepper on top and serve either warm or at room temperature.